Of the many chalices in the running for the Holy Grail, this one in Valencia Cathedral sure looks the part.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

This cemetery features modernist statues as strange as its name.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This abandoned Slovenian military barracks has become a punky-political art squat.

A whimsical bridge adorned with decorative dragons.

This one-time health resort was used by aristocrats around the world.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

This 6th-century church has the largest and best-preserved collection of Byzantine mosaics outside Constantinople.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

Those who own or stay at this 500-year-old, allegedly cursed house often meet terrible fates.

Two stone columns flank the grand Venice square, but there were supposed to be three.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

Italian poet Dante Alighieri is entombed in this small mausoleum in Ravenna, and his hometown of Florence has never been too happy about it.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

100 year tradition of fist fights, marked by marble footsteps.

Ancient snack bar of the Roman Empire re-opened.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.